A resistor has R = 10 ohms and carries I = 3 A for t = 2 s. How much heat energy q is produced?

A resistor has R = 10 ohms and carries I = 3 A for t = 2 s. How much heat energy q is produced?

• A. 90 J
• B. 270 J
• C. 360 J
• D. 180 J

Answer: (D)

Heat energy produced in a resistor comes from the power it dissipates as heat, with P = I^2 R. Over a time t, the energy is q = P t = I^2 R t. Plugging in I = 3 A, R = 10 Ω, t = 2 s gives q = (3)^2 × 10 × 2 = 9 × 10 × 2 = 180 J. You can also verify via V = IR = 30 V, then P = VI = 30 × 3 = 90 W, and q = Pt = 90 × 2 = 180 J.

Heat energy produced in a resistor comes from the power it dissipates as heat, with P = I^2 R. Over a time t, the energy is q = P t = I^2 R t. Plugging in I = 3 A, R = 10 Ω, t = 2 s gives q = (3)^2 × 10 × 2 = 9 × 10 × 2 = 180 J. You can also verify via V = IR = 30 V, then P = VI = 30 × 3 = 90 W, and q = Pt = 90 × 2 = 180 J.